A base plate for accommodating a lock is usually covered with a escutcheon for fine looking, however if the base plate doesn't fit the escutcheon in size, there are some troubles that happen such as the escutcheon frequently slips or is hard to be removed from the base plate. Recently, a screw is utilized to fix base plate and escutcheon, which not only makes escutcheon-disassembling steps become complicated and inconvenient but also affects the looking of combination structure of base plate and escutcheon.